The spherical tokamak is a recent refinement on the tokamak fusion reactor. The spherical tokamak is much tighter, resembling a cored apple rather than the conventional doughnut shape of a normal tokamak. Spherical tokamaks appear to be capable of maintaining higher temperatures and plasma densities than equivalently sized tokamaks, requiring up to ten times less current than normal tokamaks, but suffer from the simple but awkward problem that the "hole" in the centre is smaller, and therefore less equipment, most noticeably the transformer required to create a plasma current can be fitted in.